Outside of games using anti cheat, for me the most common fix is to just select Proton Hotfix or Proton Experimental in the game's compatibility settings.
For some reason certain games default to specific older Proton versions. And then of course there are a bunch of older games with a native Linux port that is now unmaintained and stopped working at some point, but they still work just fine with Proton :)
For some reason certain games default to specific older Proton versions. And then of course there are a bunch of older games with a native Linux port that is now unmaintained and stopped working at some point, but they still work just fine with Proton :)